Personality traits in wild starlings: exploration behavior and environmental sensitivity

Animal personalities, defined as consistent and correlated individual differences in behavioral traits, are suggested to be common in the animal kingdom and can have important fitness consequences. Individual differences in sensitivity to environmental cues are predicted to be part of animal personalities and are important because they will affect an individual's ability to respond to environmental change. Such environmental sensitivity as a personality trait needs further study because existing studies have rarely directly related environmental sensitivity to well-established personality traits such as exploration behavior and have focused on captive animals of specific model species. Using standardized assays of exploration behavior, we show that individual variation in 1) the speed of exploration behavior and 2) the parts of the environment that are explored are repeatable in juvenile wild starlings (Sturnus vulgaris). Environmental sensitivity was measured in separate assays and was not correlated with the speed of exploration behavior. Instead, environmental sensitivity was strongly predicted by what part of the environment was used during the preceding exploration behavior assays. Thus, in juvenile wild starlings, behavioral traits other than the speed of exploration behavior better predicted environmental sensitivity. These results suggest that the relevance of exploration behavior as a personality trait may not be easily generalized across species. Furthermore, although unrelated to exploration speed, this study illustrates how environmental sensitivity correlates with well-known personality traits and thus further highlights how animal personalities can limit behavioral phenotypic plasticity in wild populations.